Described herein are aspects generally related to communication systems, and more particularly, to rate matching in the presence of reference signals in a wireless communication system.
Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
In wireless communication systems employing LTE, a user equipment (UE) can perform rate matching for a physical downlink shared channel (PDSCH) and an enhanced physical downlink control channel (EPDCCH) received from a cell. The UE can be configured to perform the rate matching around (e.g., avoiding) known resource elements (RE) used for transmission of channel state information reference signals (CSI-RS). Correspondingly, the eNB does not map PDSCH and/or EPDCCH data for transmission in the known REs. Further, the eNB can configure the UE with locations of the REs used for CSI-RS, which may include RE locations of CSI-RS transmitted by the cell (also referred to as non-zero-power CSI-RS) as well as RE locations of CSI-RS or other signals transmitted by other cell(s) (also referred to as zero-power CSI-RS). Accordingly, the cell can utilize REs outside of the configured non-zero-power and zero-power CSI-RS REs for mapping PDSCH and/or EPDCCH communications, and the UE can accordingly rate match the PDSCH and/or EPDCCH based on REs around (e.g., not including) the non-zero-power and zero-power CSI-RS REs indicated in the configuration.
In addition, in wireless communication systems employing LTE, small cells can be heterogeneously deployed to provide increased system performance and diversity over a wireless network. Small cells may include, for example, pico cells, femto cells, and/or other types of cells having relatively lower transmit power and/or relatively smaller coverage area as compared to macro cells or macro base stations. Small cells can be turned on and off dynamically (e.g., by macro base stations or other network nodes) for inter-cell interference coordination and avoidance, load balancing, energy savings, etc. As such, small cells can transmit one or more reference signals, including cell-specific reference signals (CRS), primary synchronization signals (PSS), secondary synchronization signals (SSS), and/or configurable channel state information reference signals (CSI-RS), as discovery reference signals (DRS). In transmitting one or more of the reference signals as DRS, the small cell may utilize a maximum allowed measurement bandwidth, which can be less than a system bandwidth. User equipment (UEs) can accordingly discover small cells that are turned on based at least in part on receiving one or more of the DRSs.
When CSI-RS is transmitted as a DRS, the associated configuration received for the CSI-RS may not be explicit as to whether non-zero-power and/or zero-power CSI-RSs used for DRS are transmitted over the entire system bandwidth or over the maximum allowed measurement bandwidth, which may lead to undesirable results in performing rate matching for PDSCH and/or EPDCCH.